NASA Cassini Significant Events for 01/16/2013 - 01/22/2013

Cassini is orbiting Saturn with a period of 13.3 days in a plane inclined 53 degrees from the equatorial. The most recent spacecraft tracking and telemetry data were collected on Jan. 15 by a 34-meter Deep Space Network station at Canberra, Australia. Except for some science instrument issues described in previous reports, the spacecraft continues to be in an excellent state of health with all of its subsystems operating normally. Information on the present position of the Cassini spacecraft may be found on the "Present Position" page at: http://saturn.jpl.nasa.gov/mission/presentposition/ .

Flight team members gave Cassini-Huygens Program Manager Bob Mitchell a warm sendoff at his well-attended retirement party in JPL's Von Karman Auditorium on Wednesday evening. Mitchell leaves JPL after 47 years of distinguished service, including more than 14 years at the helm of Cassini-Huygens. A recent photograph of him may be seen here: http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=4487 .

Wednesday, Jan. 16 (DOY 016)

The Imaging Science Subsystem (ISS) created a 15.5-hour movie of the dark face of the rings to search for periodicities in the spokes which are the curious radial features first observed by Voyager (see http://go.usa.gov/4WGP). The Composite Infrared Spectrometer (CIRS) then began a ten-hour observation of the rings while in Saturn's shadow to study their thermal inertia.

Thursday, Jan. 17 (DOY 017)

The radar instrument turned the high-gain antenna to Titan, 1.6 million kilometers away, to conduct a distant radiometry calibration for two hours. ISS made a five-hour D ring observation to monitor time-variable structures, including corrugation in the outer D ring and the structures produced by magnetospheric asymmetries. The Visible and Infrared Mapping Spectrometer (VIMS), ISS and CIRS then started a four-hour F ring observation at high-phase illumination.

Today and again on Saturday, the Attitude and Articulation Control Subsystem team executed Reaction Wheel Assembly bias maneuvers to adjust wheel speeds while thrusters stabilized the spacecraft.

The Radio and Plasma Wave Science subsystem used its direction-finding capability to survey Saturn's inner magnetosphere. This observation was repeated on Friday.

The Radio Science team conducted a Saturn gravity-science enhancement observation today, and again after periapsis passage on Saturday, using a 34-meter DSN station in California to measure the Doppler shifts induced in Cassini's X-band and Ka-band signals.

The Radio Science team carried out a ring ingress occultation experiment. Cassini's X-band transponder locked onto a stable-frequency uplink provided by the 70-meter Deep Space Network (DSN) antenna in Spain and generated phase-coherent downlink signals at S, X, and Ka-band radio frequencies. The spacecraft then passed behind Saturn's F ring, A ring, and B ring before disappearing behind the planet. The occultation geometry was ideally suited for profiling density and bending waves in the A ring and for providing additional constraints on the kinematics of circular and non-circular features in Cassini Division and outer edge of the B ring. The measurements will also be used to determine or constrain particle size distribution in resolved ring features and physical properties of gravitational wakes in the outer B ring and the entire A ring.

Following the radio science experiment, ISS, CIRS, UVIS and VIMS observed Enceladus's plume for two hours.

The Cosmic Dust Analyzer took control of spacecraft pointing for eight hours while Cassini crossed Saturn's ring plane at about 440,000 kilometers above the atmosphere. Next, CIRS observed the rings while in Saturn's shadow to study their thermal inertia. ISS then began an eight-hour search for moonlets in gaps in the C ring; it is thought possible that such moonlets may be holding the gaps open.

Saturday, Jan. 19 (DOY 019)

VIMS observed an ingress occultation of the star W Hydrae as it made a radial pass across the entire ring system before going behind Saturn. This observation was intended to study azimuthal variations of non-circular ring features, the F ring, and the Encke Gap ringlets. The day concluded with a one-hour ISS observation to reacquire and track known "propellers" which are small objects that create visible wakes in adjacent rings. These retargeting observations help maintain temporal resolution of propeller orbital evolution.

Cassini passed through periapsis going 41,668 kilometers per hour relative to Saturn, at about 389,000 kilometers above the atmosphere.

Sunday, Jan. 20 (DOY 020)

CIRS performed radial scans of the rings for six hours in order to further map them at various phases and latitudes. These will assist efforts to model the rings' directional emissivity. ISS then created a five-hour high-resolution radial scan of the illuminated side of the main rings. VIMS, CIRS and UVIS watched a rare radial passage of the anti-solar point across the whole right ansa of the rings to map out the rings' opposition effect between phase angles of 0 and 1.0 degrees. (The opposition effect is the surge in brightness of a grainy surface as the phase angle approaches zero.) The busy period around periapsis concluded with another seven-hour radial scan by CIRS.